40 Latest Chemistry Basic and Tough Quiz Questions Answers

1. The modern atomic mass unit is based on ____
Answer: Carbon-12.

2. The total number of electrons present in 18 ml of water is ____
Answer: 6.02 × 1024.

3. 3 g of a salt of molecular weight 30 is dissolved in 250 g of water. The molality of the solution is ____
Answer: 0.4m.

4. The weight of 1 × 1022 molecules of CuSO4 .5H2O is ____
Answer: 4.14 g.

5. 27 g of Al will react completely with how many grams of oxygen?
(a) 8 g (b) 16 g (c) 32 g (d) 24 g
Answer: D.

6. A compound was found to contain nitrogen and oxygen in the ratio 28 gm and 80 gm respectively. The formula of compound is
(a) NO (b) N2O3 (c) N2O5 (d) N2O4
Answer: C.

7. The largest number of molecules is in
(a) 36 g of water (b) 28 g of carbon monoxide (c) 46 g of ethyl alcohol (d) 54 g of nitrogen pentoxide
Answer: A.

8. The total number of electrons in one molecule of carbon dioxide is
(a) 22 (b) 44 (c) 66 (d) 88
Answer: A.

9. A gaseous mixture contains oxygen and nitrogen in the ratio of 1: 4 by weight. Therefore the ratio of their number of molecules is
(a) 1: 4 (b) 1: 8 (c) 7: 32 (d) 3: 16
Answer: C.

10. 2.76 g of silver carbonate on being strongly heated yields a residue weighing
(a) 2.16 g (b) 2.48 g (c) 2.32 g (d) 2.64 g
Answer: A.

11. M is molecular weight of KMnO4. The equivalent weight of KMnO4 when it is converted into K2MnO4 is
(a) M (b) M/3 (c) M/5 (d) M/7
Answer: A.

12. If 0.50 mole of BaCl2 is mixed with 0.20 mol of Na3 PO4, the maximum number of moles of Ba3 (PO4) 2 that can be formed is
(a) 0.70 (b) 0.50 (c) 0.20 (d) 0.10
Answer: D.

13. One mole of N2H4 loses ten moles of electrons to form a new compound Y. Assuming that all the nitrogen appears in the new compound, what is the oxidation state of nitrogen in Y? (There is no change in the oxidation state of hydrogen).
(a) –1 (b) –3 (c) +3 (d) +5
Answer: C.

14. The oxidation number of carbon in CH2O is
(a) – 2 (b) + 2 (c) 0 (d) + 4
Answer: C.

15. A molal solution is one that contains one mole of a solute in:
(a) 1000 g of the solvent (b) one litre of the solvent (c) one litre of the solution (d) 22.4 litres of the solution
Answer: A.

16. In which mode of expression, the concentration of a solution remains independent of temperature?
(a) Molarity (b) Normality (c) Formality (d) Molality
Answer: D.

17. An aqueous solution of 6.3 g oxalic acid dihydrate is made up to 250 ml. The volume of 0.1 N NaOH required to completely neutralize 10 ml of this solution is
(a) 40 ml (b) 20 ml (c) 10 ml (d) 4 ml
Answer: A.

18. Which has maximum number of atoms?
(a) 24g of C (12) (b) 56g of Fe (56) (c) 27g of Al (27) (d) 108g of Ag (108)
Answer: A.

19. Consider a titration of potassium dichromate solution with acidified Mohr’s salt solution using diphenylamine as indicator. The number of moles of Mohr’s salt required per mole of dichromate is
(a) 3 (b) 4 (c) 5 (d) 6
Answer: D.

20. What weight of AgCl will be precipitated when a solution containing 4.77 g of NaCl is added to a solution of 5.77 g of AgNO3?
Answer: 4.87 g.

General Chemistry Online Tough Quiz Answers

21. One gram of an alloy of aluminium and magnesium when treated with excess of dil. HCl forms magnesium chloride, aluminium chloride and hydrogen. The evolved hydrogen, collected over mercury at 0°C has a volume of 1.20 litres at 0.92 atm. pressure. Calculate the composition of the alloy. [H = 1, Mg = 24, Al = 27]
Answer: Al 54.87%, Mg 45.13%.

22. 4.215 g of a metallic carbonate was heated in a hard glass tube and the CO2 evolved was found to measure 1336 ml at 27°C and 700 mm pressure. What is the equivalent weight of the metal?
Answer: 8.38.

23. 5 ml of a gas containing only carbon and hydrogen were mixed with an excess of oxygen (30 ml) and the mixture exploded by means of an electric spark. After the explosion, the volume of the mixed gases remaining was 25 ml. On adding a concentrated solution of potassium hydroxide, the volume further diminished to 15 ml of the residual gas being pure oxygen. All volumes have been reduced to N.T.P. Calculate the molecular formula of the hydrocarbon gas.
Answer: CH4.

24. In the analysis of 0.500 g sample of feldspar, a mixture of chlorides of sodium and potassium is obtained which weighs 0.1180g. Subsequent treatment of mixed chlorides with silver nitrate gives 0.2451g of silver chloride. What is the percentage of sodium oxide and potassium oxide in feldspar?
Answer: Na2O = 3.58%, K2O = 10.62%.

25. A compound contains 28 percent of nitrogen and 72 percent of metal by weight. 3 atoms of metal combine with 2 atoms of N. Find the atomic weight of metal.
Answer: 24.

26. A hydrocarbon contains 10.5g of carbon per gram of hydrogen. 1 litre of the vapour of the hydrocarbon at 127°C and 1 atmosphere pressure weighs 2.8g. Find the molecular formula.
Answer: C7H8.

27. Five ml of 8N nitric acid, 4.8 ml of 5N hydrochloric acid and a certain volume of 17M sulphuric acid are mixed together and made upto 2litre. Thirty ml. of this acid mixture exactly neutralise 42.9 ml of sodium carbonate solution containing one gram of Na2CO3 .10H2O in 100 ml. of water. Calculate the amount in gram of the sulphate ions in solution.
Answer: 6.3648 g.

28. A sample of hydrazine sulphate (N2H6 SO4) was dissolved in 100 ml. of water, 10 ml of this solution was reacted with excess of ferric chloride solution and warmed to complete the reaction. Ferrous ion formed was estimated and it required 20 ml. of M/50 potassium permanganate solution. Estimate the amount of hydrazine sulphate in one litre of the solution.
Answer: 6.5 g.

29. An equal volume of a reducing agent is titrated separately with 1M KMnO4 in acid neutral and alkaline media. The volumes of KMnO4 required are 20 ml. in acid, 33.4 ml. neutral and 100 ml. in alkaline media. Find out the oxidation state of manganese in each reduction product. Give the balanced equations for all the three half reactions. Find out the volume of 1M K2Cr2O7 consumed; if the same volume of the reducing agent is titrated in acid medium.
Answer: +2, +4, +6, 16.66 ml.

30. A mixture of H2C2O4 (oxalic acid) and NaHC2O4 weighing 2.02 g was dissolved in water and solution made upto one litre. Ten millilitres of the solution required 3.0 ml. of 0.1 N sodium hydroxide solution for complete neutralization. In another experiment, 10.0 ml. of the same solution, in hot dilute sulphuric acid medium. require 4.0 ml. of 0.1 N potassium permanganate solution for complete reaction. Calculate the amount of H2C2O4 and NaHC2O4 in the mixture.
Answer: 1.12 g, 0.90 g.

31. A solid mixture (5.0 g) consisting of lead nitrate and sodium nitrate was heated below 600ºC until the weight of the residue was constant. If the loss in weight is 28.0 per cent, find the amount of lead nitrate and sodium nitrate in the mixture.
Answer: 3.324 g, 1.676 g.

32. Calculate the molality of 1 litre solution of 93% H2 SO4 (weight/volume). The density of the solution is 1.84 g/ml.
Answer: 10.43 m.

33. A 1.0 g sample of Fe2O3 solid of 55.2% purity is dissolved in acid and reduced by heating the solution with zinc dust. The resultant solution is cooled and made upto 100.0 ml. An aliquot of 25.0 ml of this solution requires 17.0 ml of 0.0167 M solution of an oxidant for titration. Calculate the number of electrons taken up by the oxidant in the reaction of the above titration.
Answer: 6.

34. A 2.0 g sample of a mixture containing sodium carbonate, sodium bicarbonate and sodium sulphate is gently heated till the evolution of CO2 ceases. The volume of CO2 at 750 mm Hg pressure and at 298 K is measured to be 123.9 ml. A 1.5g of the same sample requires 150 ml. of (M/10) HCl for complete neutralisation. Calculate the% composition of the components of the mixture.
Answer: Na2 CO3 -26.5%, Na2SO4 -31.5%.

35. Upon mixing 45.0 ml. of 0.25 M lead nitrate solution with 25.0 ml of 0.10 M chromic sulphate solution, precipitation of lead sulphate takes place. How many moles of lead sulphate are formed? Also, calculate the molar concentrations of the species left behind in the final solution. Assume that lead sulphate is completely insoluble.
Answer: 0.0075 M, Pb2+ = 0.05357 M, NO3 – = 0.3214 M, Cr3+ = 0.0714 M.

36. An aqueous solution containing 0.10 g KIO3 (formula weight = 214.0) was treated with an excess of KI solution. The solution was acidified with HCl. The liberated I2 consumed 45.0 mL of thiosulphate solution to decolourise the blue starch-iodine complex. Calculate the molarity of the sodium thiosulphate solution.
Answer: 0.062.

37. How many millilitres of 0.5 M H2 SO4 are needed to dissolve 0.5 g of copper(II) carbonate?
Answer: 8.097 ml.

38. A plant virus is found to consist of uniform cylindrical particles of 150 Å in diameter and 5000 Å long. The specific volume of the virus is 0.75 cm3/g. If the virus is considered to be a single particle, find its molar mass.(1999 – 3 Marks)
Answer: 7.09 × 107.

39. Hydrogen peroxide solution (20 ml) reacts quantitatively with a solution of KMnO4 (20 ml) acidified with dilute H2SO4. The same volume of the KMnO4 solution is just decolourised by 10 ml of MnSO4 in neutral medium simultaneously forming a dark brown precipitate of hydrated MnO2. The brown precipitate is dissolved in 10 ml of 0.2 M sodium oxalate under boiling condition in the presence of dilute H2SO4. Write the balanced equations involved in the reactions and calculate the molarity of H2O2. (2001 – 5 Marks)
Answer: 0.1.

40. Calculate the molarity of water if its density is 1000 kg/m3.
Answer: 55.55 M.


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